I'm hoping someone could help me with a marriage lookup or even Birth

I've checked many Irish resources but my Irish roots are a fairly new discovery so i'm not sure i'm researching where i should be. I've tried the Griffiths Valuation, familysearch and a couple of others i cant recall but my main problem is the different spellings of the name....
Well here is what i have and known to be accurate (ish)!!
Michael LINAHAN (I've lost count how many variations of the name i've discovered) married Mary Both of Dungarvan, Co Waterford
Michael b. abt 1841 Mary b. abt 1844
They had atleast 4 children who were born in Dungarvan
David b.1865
Statia (i assume this is short for Annastatia) b.1867
Kate b. 1870
Minnie b. 1872
They had three more children but they were born in Wales. But this is where it gets interesting...Sometime during the 1880's they ALL changed their name to LEONARD??
It has been Leonard ever since, so now i'm not entirely convinced their name was Linahan (sp) to begin with. However they are on the Wales 1881 census as Linahan. Why would they change their name? And how am i suposed to find them.
Please, plaese, please any help or tips greatly appreciated as i'm at a loss.
PS..apologies if i'm not making any sense, its been a long day infront of the pc